Year in Review: Planck refines cosmic history

Satellite hints at slower expansion rate for universe

CHANGING TEMPS A color-coded map shows fluctuations in microwave radiation temperature across the sky recorded by the Planck satellite. Noteworthy features include differences between hemispheres and a cold spot (circle at right).

In October, astronomers said good-bye to the European Space Agency’s Planck satellite, breaking off contact with the source of the most precise measurements yet of the universe’s oldest light.

Planck had finished its mission to measure the Big Bang’s remnant radiation, which today constitutes an invisible bath of microwaves permeating the cosmos. This ancient radiation has cooled over time to less than 3 kelvins (degrees above absolute zero). Its precise temperature varies ever so slightly from point to point across the sky.

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